Use of policy information provided by customers to control utilization of data processing resources is well known within the industry. For example, the Data Facilities Product (DFP) Systems Managed Storage (SMS) product from International Business Machines Corporation provides for the definition of policy information to control the placement and management of data sets on DASD. SMS policy support is described in DFSMS/MVS 1.1 Storage Administration Reference for DFP (SC26-4920), Chapters 2, 11 and 15, which is incorporated herein by reference in its entirety.
The SMS documentation describes the manner in which customers control a DASD configuration. In particular, there is a control data set called COMMDS (communication data set) that is shared and accessed by all systems in a SMS configuration. Each of the participating systems access COMMDS on a default of 15 secs (which can be changed from 1 to 999 secs). Inactive policies are kept in a data set called SCDS (Source Control Data Set). This is validated and activated through interactive programming services or operator command on any one of the systems in the configuration.
The process of activation puts the active policy in another data set called ACDS (Active Control Data Set) and records the change of the configuration in the COMMDS. All systems, when they access the COMMDS, recognize this and use the new ACDS and COMMDS. ACDS is also shared by all processors in a configuration. Therefore, there is a single policy that is active, is changeable through command from any system, is system wide and does not require system reinitialization. Some operator commands will result in updating ACDS and COMMDS. But, to add new processors, storage groups, volumes or libraries, the interactive programming services must be used to add, delete, or remove entries in an SCDS, validate and activate the new policy. If the validation step fails, the old configuration is retained. Because of the validation, there can be nothing incompatible between the old configuration and the new configuration defined by policy. The old set (SCDS, ACDS and COMMDS) is not checked with the new set.
There is no duplication of information in SMS between the ACDS and control information stored on DASD. Therefore, if the COMMDS or ACDS become unusable, the user can allocate a new one and copy the information from the SCDS, or activate the same or a different SCDS. SMS also keeps an in-storage copy of ACDS. Therefore, if an ACDS becomes unusable, all systems can continue to work.
Several disadvantages are associated with the current mechanisms for managing permanent storage facilities. Notably, the current techniques do not assist in reclaiming storage areas when those areas are no longer needed and processing associated with policies which are used to direct allocation of storage areas assume that no errors have been made by the system's administrator.
Reclaim of storage areas occurs outside the current mechanisms for storage allocation policy management. There are no current facilities for tracking the set of users associated with an allocated storage area, no processing for maintaining the status of users of an allocated storage area at the storage facility, and no capabilities for insuring reclaim of storage areas no longer needed occurs in a timely way and transparently to users of the storage area should changes in the configuration make it not possible to access the storage facility at the time a storage area is to be released. As there currently does not exist any mechanism for tracking users of a storage area, nor management of resource re-use, there are no facilities for managing delays in reclaiming storage areas nor any possible inconsistencies between policy information regarding storage areas in use and their users, and the status recorded at the storage facility.
As it is always assumed that any and all changes made by the systems administrator are to take immediate effect, there is no management of incompatible changes nor pending policy changes.